[A case report of acute encephalitis with neuro-psychiatric side-effects of acyclovir]

We reported a 5-year-old boy with acute encephalitis due to suspected herpes simplex infection, who developed confusion, agitation and insomnia during intravenous administration of acyclovir. He recovered from these neuro-psychiatric symptoms two days after the cessation of acyclovir. The same symptoms recurred two days after its re-administration and resolved on the next day of the second cessation of the drug. Electroencephalogram (EEG) showed periodic lateralized epileptiform discharges (PLEDs) on hospital day 16, which disappeared on hospital day 27, suggesting that neurotoxicity of acyclovir may induce PLEDs. Although acyclovir is useful for the treatment of herpes simplex and varicella-zoster virus infections, we have to pay attention to its neurotoxicity.